Hayne's future is uncertain after he was cut from the Fiji Rugby Sevens squad, quashing his Olympic dream.

He was been linked with a return to the Eels - the club he quit to pursue a career in the NFL in late 2014 - as early as this month.

Skipper Kieran Foran's decision to quit the embattled club, to address personal issues, has seemingly opened the door for the Eels to fit Hayne under the salary cap for the rest of the season.

However St George Illawarra playmaker Marshall said it wouldn't be right for the NRL to rubber stamp Hayne's contract because Foran was already set to miss the rest of the year with a shoulder injury and his salary should still count towards their cap.

"First of all they'd have to be under the cap to do that, but I don't think they could fit him under the cap in their current situation," former Kiwis captain Marshall said on Fox Sports' NRL 360 on Tuesday night.

"Kieran Foran was out for the season already through injury. How could they wipe him off the cap this year?

"If he's wiped off the cap next year and so on, then fair enough. But for the rest of this year he wasn't going to be playing anyway."

Marshall, who played six Super Rugby games for the Auckland Blues after quitting the NRL in 2014, said he doubted any NRL club would be able to sign Hayne because his worth would have sky rocketed over the past 18 months.

As much as Marshall admitted he'd like to see Hayne back in rugby league, he doubted NRL clubs had the hip pockets to compete with cashed-up European rugby union.

"In terms of him coming back to the game, there's going to be a lot of money offered from rugby," Marshall said.